Question about Voicechat in MixedRealityToolkit-Unity Sharing

Hello! I am using the latest VoiceChat scripts from MixedRealityToolkit-Unity, but I am only hearing my own voice.
I am using the SharingTest scene which in the Assets\HoloToolkit-Examples\Sharing\SharingService\Scenes.And i attached both MicrophoneReceiver.cs and MicrophoneTransmitter.cs onto MixedRealityCamera.Then i launch the Sharing Service and use two hololens to successfully connect to the server. But i can only hear my own voice in hololens,can't hear other's voice.(my unity version is 2017.2.0f3)
How can i Setting to sovle the problem?
Thanks for any help!